Instructions for drilled pilingDesign and execution guide

FINNRAHelsinki 2003

Instructions for drilled pilingDesign and execution guide

Guidelines for design and implementation

ISBN 951-803-026-XTIEH 2000002E-03 (Guidelines for design and implementation)

Internet (www.finnra.fi/julkaisut) pdfISBN 951-803-027-8TIEH 2000002E-v-03 (Guidelines for design and implementation)

Edita Prima OyHelsinki 2003

Finnish Road AdministrationOpastinsilta 12 APB 33FIN-00521 HELSINKIPhone int. +358 204 22 11

2/68 FOREWORD Drilled piles and piling have been developed significantly in recent years which has increased their use. Yet, there have been no national guidelines for drilled piling in Finland. Consequently, builders have applied the information contained in the Driven piling instructions (LPO-87) and the High-capacity piling instructions (SPO-2001). These manuals do not, however, sufficiently cover the details of drilled piling. These instructions for drilled piling are only provisional. It will be revised in 3-5 years, as soon as further experiences and research results from drilled piling have been collected. In connection with the revision, these instructions may be incorporated into revised instructions for piling. The members of the steering group for these instructions have included: Juha Heinonen, LicTech, Oy VR-Rata Ab (chairman); Sami Eronen, LicTech, Rautaruukki Oyj/Metform; Jouko Lehtonen, LicTech, Rautaruukki Oyj/CRD; Esko Palmu, B.Sc. (Eng), Bridge Unit of the Road Administration; Pentti Salo, M.Sc. (Eng), Road and Traffic Engineering Unit of the Road Administration; Pekka Mantere, M.Sc. (Eng), Suomalainen Insinritoimisto Oy and Professor Jorma Hartikainen and Pasi Korkeakoski, LicTech, the Laboratory of Foundation and Earth Structures at Tampere University of Technology. The instructions were commissioned from the Laboratory of Foundation and Earth Structures at Tampere University of Technology (TUT). The funding comes from the Rail Administration, Rautaruukki Oyj and the Road Administration. The R&D on drilled piling has been conducted primarily by the Geotechnical Laboratory at TUT, and the following masters and licentiate theses and publications have been used as source material for the instructions: Sami Eronen, Drilled Piles in Scandinavia (1997); Henning Muhra, Micropiles in Northern and Middle Europe (1997); Jouni Mali, Rautateiden shkistyspylvn kaksoisputkiperustus (1999); Marko ljymki, Porapaalumenetelmn soveltaminen vaakakuormitetuissa rakenteissa (1997); Jyrki Kataja, Drilled Pile Execution by Dual Fluid Systems (2000) and Sami Eronen, Drilled Piles in Underpinning and Bridge Foundations (2001).

3/68 Table of contents 1 PILES COVERED BY INSTRUCTIONS AND REQUIREMENTS OF PILING SITE............................ 6

1.1 Applicability of instructions.............................................................................................................. 6 1.2 Types of drilled piles ....................................................................................................................... 6

1.2.1 Steel core pile........................................................................................................................... 6 1.2.2 Drilled steel pipe pile whose casing becomes part of pile ....................................................... 8 1.2.3 Drilled steel pipe pile whose casing is withdrawn.................................................................... 9 1.2.4 Grouted drilled piles ............................................................................................................... 10

1.3 Requirements of piling site .......................................................................................................... 11 2 STATUS OF INSTRUCTIONS ............................................................................................................ 12

2.1 General.......................................................................................................................................... 12 2.2 Rules, regulations and standards for design ................................................................................ 12 2.3 Standards ...................................................................................................................................... 13 2.4 National standards and regulations .............................................................................................. 15

3 DEFINITIONS ...................................................................................................................................... 17 4 REQUIRED PILING DOCUMENTATION............................................................................................ 20

4.1 Documentation required for regular piling ................................................................................... 20 4.2 Further documentation required for foundation strengthening.................................................... 20

5 GROUND INVESTIGATIONS ............................................................................................................. 21 5.1 Requirements ................................................................................................................................ 21 5.2 Easy sites ...................................................................................................................................... 22

5.2.1 Piles bearing on rock.............................................................................................................. 22 5.2.2 Piles bearing on ground........................................................................................................ 22 5.2.3. Horizontally loaded piles ....................................................................................................... 22

5.3 Demanding sites............................................................................................................................ 22 5.3.1 Piles bearing on rock.............................................................................................................. 22 5.3.2 Piles bearing on ground ......................................................................................................... 22 5.3.3 Horizontally loaded piles ........................................................................................................ 23

5.4 Very demanding sites.................................................................................................................... 23 5.4.1 General ................................................................................................................................... 23 5.4.2 Piles bearing on rock.............................................................................................................. 23 5.4.3 Piles bearing on ground ......................................................................................................... 23 5.4.4 Horizontally loaded piles ........................................................................................................ 24

5.5 Presentation of ground investigations........................................................................................... 24 6 PILE MATERIALS AND REINFORCEMENTS.................................................................................... 25

6.1 General.......................................................................................................................................... 25 6.2 Ingredients of concrete, mortar and grouts................................................................................... 25

6.2.1 Cement and substitute additives............................................................................................ 25 6.2.2 Aggregate ............................................................................................................................... 25 6.2.3 Water ...................................................................................................................................... 26 6.2.4 Admixtures.............................................................................................................................. 26

6.3 Concrete ........................................................................................................................................ 26 6.3.1 General ................................................................................................................................... 26 6.3.2 Mixing of ingredients .............................................................................................................. 27 6.3.3 Compliance verification of concrete ....................................................................................... 28

6.4 Mortars .......................................................................................................................................... 28 6.5. Grouts........................................................................................................................................... 29

6.5.1 General ................................................................................................................................... 29 6.5.2 Determination of compliance.................................................................................................. 29

6.6 Other substances used in drilling ................................................................................................ 29 6.7 Steels ........................................................................................................................................... 29

6.7.1 General ................................................................................................................................... 29 6.7.2 Reinforcement steels.............................................................................................................. 30

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6.7.3 Structural sections .................................................................................................................. 30 6.8 Joints ............................................................................................................................................ 30

6.8.1 General ................................................................................................................................... 30 6.8.2 Extension of piles by welding ................................................................................................. 30

7 DESIGN ............................................................................................................................................... 32 7.1 General.......................................................................................................................................... 32 7.2 Tasks included in the design......................................................................................................... 32 7.3 Limit states and dimensioning mechanisms to be considered..................................................... 32 7.4 Geotechnical design of piles ......................................................................................................... 33

7.4.1 General ................................................................................................................................... 33 7.4.2 Calculation of geotechnical bearing capacity......................................................................... 33 7.4.3 Base resistance of piles bearing on rock .............................................................................. 34 7.4.4 Shaft resistance of piles bearing on rock............................................................................... 34 7.4.5 Bearing capacity of pile bearing on ground ........................................................................... 35 7.4.6 Tensile capacity of pile ........................................................................................................... 35 7.4.7 Lateral capacity of pile............................................................................................................ 37 7.4.8 Dimensioning for a cyclic load................................................................................................ 37 7.4.9. Determining geotechnical bearing capacity of pile by static loading tests ........................... 37

7.5. Structural design .......................................................................................................................... 37 7.5.1. General .................................................................................................................................. 37 7.5.2. Corrosion of shaft-grouted piles ............................................................................................ 38 7.5.3 Corrosion allowance of steel-surfaced drilled piles ............................................................... 39 7.5.4 Structural dimensioning.......................................................................................................... 40

7.5.4.1 General ............................................................................................................................ 40 7.5.4.2 Buckling capacity ............................................................................................................. 40 7.5.4.3 Lateral pressure caused by buckling............................................................................... 41 7.5.4.4 Structural capacity ........................................................................................................... 44

7.5.5 Vertical pile displacements..................................................................................................... 44 7.6 Position of piles ............................................................................................................................. 45

7.6.1 Permissible deviations in pile positioning .............................................................................. 45 7.6.2 Pile positions .......................................................................................................................... 46

7.6.2.1 Distance between piles.................................................................................................... 46 7.6.2.2 Distances between piles and other structures ................................................................ 46

7.7 Drilling of piles ............................................................................................................................... 47 7.8 Reinforcement ............................................................................................................................... 47

7.8.1.1 General ............................................................................................................................ 47 7.8.1.2 Main rebars ...................................................................................................................... 47 7.8.1.3 Stirrups............................................................................................................................. 47 7.8.1.4 Special reinforcements .................................................................................................... 48

8 PILING WORK ..................................................................................................................................... 49 8.1 Work and quality plan.................................................................................................................... 49 8.2 Requirements for the implementers of the piling work ................................................................. 50

8.2.1 Piling supervisor ..................................................................................................................... 50 8.2.2 Tasks of the piling work supervisor........................................................................................ 50

8.3 Piling work ..................................................................................................................................... 50 8.4 Different installation methods........................................................................................................ 51

8.4.1 Drilling equipment................................................................................................................... 51 8.4.1.1 General ............................................................................................................................ 51 8.4.1.2 Top hammer equipment ................................................................................................. 52 8.4.1.3 DTH equipment................................................................................................................ 52

8.4.2 Drilling method........................................................................................................................ 52 8.4.2.1 The eccentric drilling method........................................................................................... 52 8.4.2.2 The concentric drilling method ........................................................................................ 53

8.5 Drilling of a pile.............................................................................................................................. 53

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8.6 Flushing during drilling .................................................................................................................. 55 8.7 Joint ............................................................................................................................................... 55 8.8 Grouting......................................................................................................................................... 56

8.8.1 General ................................................................................................................................... 56 8.8.2 Grouting in soil layers............................................................................................................. 56

8.8.2.1 General ............................................................................................................................ 56 8.8.2.2 Shaft grouting................................................................................................................... 57 8.8.2.3 Base grouting................................................................................................................... 57

8.8.3 Grouting in rock ...................................................................................................................... 57 8.9 Closing of pile heads and cutting of piles ..................................................................................... 57 8.10 Cleaning ...................................................................................................................................... 57 8.11 Reinforcement ............................................................................................................................. 57 8.12 Concreting of piles ...................................................................................................................... 57

9 QUALITY CONTROL AND MEASUREMENTS .................................................................................. 59 9.1 Quality control ............................................................................................................................... 59 9.2 Piling work monitoring ................................................................................................................... 59 9.3 Testing of piles .............................................................................................................................. 60

9.3.1 General requirements............................................................................................................. 60 9.3.2 Special requirements.............................................................................................................. 60

10 DOCUMENTATION OF THE PILING WORK ................................................................................... 61 11 LABOUR PROTECTION AND ENVIRONMENTAL CONTROL ....................................................... 63

11.1 Labour protection ........................................................................................................................ 63 11.2 Environmental impacts of piling .................................................................................................. 63

11.2.1 General ................................................................................................................................. 63 11.2.2 Vibration................................................................................................................................ 63 11.2.3 Noise..................................................................................................................................... 63 11.2.4 Discharges............................................................................................................................ 63

APPENDICES: MODEL PILING RECORDS

6/68 1 PILES COVERED BY INSTRUCTIONS AND REQUIREMENTS OF PILING SITE

1.1 Applicability of instructions These instructions present the general principles of the design and execution of drilled piles. The cross-section of the piles in question is round. The instructions apply to individual piles and groups of piles. The drilled-pile types covered by the instructions: steel core pile drilled steel pipe pile whose casing becomes part of the structure drilled steel pipe pile whose casing is withdrawn grouted drilled piles The instructions do not deal with auger-bored cast-in-place piles. The drilled-pile-types differ from each other, but are all suitable if: the construction site has layers that are difficult to penetrate the rock face is sharply inclined piles must reach a certain depth of penetration the surrounding structures are sensitive to vibration accurate positioning is a must. In Finland, drilled piles are generally implemented as end-bearing piles bearing on rock which allows efficient utilisation of the strength of pile materials. Vertically loaded drilled piles bearing on soil layers are used when the coarse-grained soil layer or moraine layer above the bedrock is thick. Drilled piles that are primarily horizontally loaded are generally supported by soil layers. Drilled piles are not used as cohesion piles.

1.2 Types of drilled piles

1.2.1 Steel core pile Thin-walled pile casings are used for drilling traditional steel core piles. The casing is extended if necessary. When bedrock is reached, the pilot bit used to drill through the soil is extracted, and drilling is continued using a rock bit which does not sink the casing. After drilling is completed, the casing is flushed and filled with grout. Finally, a round bar equipped with a centralizer is installed in the casing (Figure 1 and 2). Drilling may be done either by a top hammer or a DTH hammer applying a concentric or an eccentric drilling method.

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Fig. 1. Installation phases of a steel core pile.

Fig. 2. Cross-section of steel core pile.

B/455/Pora./fig01

dg

dst

Thin-walled casing

Steel rod

Mortar

B/455/Pora./fig02

8/68 1.2.2 Drilled steel pipe pile whose casing becomes part of pile The thick-walled steel pipe pile functions as a casing during drilling and as a bearing structure that takes part of the pile load of the finished drilled pile. The casing is extended if necessary. Rock drilling is implemented with the same equipment without separate work phases (Figure 4). The pipe is flushed after drilling. In case a reinforcement cage is used, it is installed in the casing prior to concreting. Drilling may be done as with steel core piles either with a top hammer or a DTH hammer applying a concentric or an eccentric drilling method. Different types of reinforcements may also be used depending on pile loads and soil conditions (Figure 3).

Fig. 3. Reinforcement alternatives for drilled steel pipe piles when the casing becomes part of

the pile.

Fig. 4. Installation phases of a drilled steel pipe pile whose casing becomes part of the pile.

dst = dg

Casing Reinforcement Concrete or mortar

B/455/Pora./fig03

dst = dg dst = dg dst = dg

B/455/Pora./fig04

9/68 1.2.3 Drilled steel pipe pile whose casing is withdrawn In the case of a drilled steel pipe pile whose casing is extracted, the steel pipe functions as a casing during drilling. The installation of a drilled steel core pile is described in Figure 6. Drilling may be done either by a top hammer or a DTH hammer as with the steel core pile. A pile must always be reinforced. Different reinforcement types can be used with drilled piles depending on loads and soil conditions (Figure 5).

Fig. 5. Alternative reinforcements for drilled steel pipe piles when the casing is withdrawn.

Fig. 6. Installation phases of a drilled steel pipe pile whose casing is withdrawn.

dst = dg

ReinforcementConcrete or mortar

B/455/Pora./fig05

dst = dg dst = dg

B/455/Pora./fig06

10/68 1.2.4 Drilled piles grouted through the bearing element In the case of drilled piles grouted through the bearing element the drill rod remains in the ground and the shaft is grouted with mortar during drilling. Piles are drilled using top hammer equipment. Drill rods are generally extended using threaded sleeves. In principle, pile installation involves only a single work phase: simultaneous drilling and grouting (Figure 7). Flushing is effected through the hole in the middle of the drill rod using mortar. When the drill bit is larger in diameter than the drill rod, the pile gets a shell of grout equal to the diameter of the drill bit depending on the soil, flushing pressure and extent and drilling speed. The wall of the drill hole receives a mortar layer that supports the hole. Depending on the soil, a zone of mixed mortar and soil may form outside the cement layer. In structural dimensioning, only the capacity of the drill rod can be taken into account. In buckling dimensioning, the width of the soil layer supporting the pile can be considered equal to the diameter of the drill bit. In geotechnical dimensioning, a grouted shaft equal to the diameter of the drill bit may be taken into account. The consideration of the zone of mixed cement slurry and soil in geotechnical dimensioning requires procedural tests and loading tests at the piling site or, at least, in comparable soil conditions near the site (Figure 8).

Fig. 7. Installation phases of a drilled pile grouted through the bearing element. Pile bearing on

rock (A) and pile bearing on ground (B).

A B

B/455/Pora./fig07

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Fig. 8. Cross-section of a drilled pile grouted through the bearing element.

1.3 Requirements of piling site Based on the Foundation engineering instructions of 1988, piling sites can be divided into three categories: easy, demanding and very demanding. The requirements of a site are determined on the basis of the superstructure, soil conditions and degree and direction of loading. The requirements of the superstructure are defined as follows: Easy projects

Light, basic structures: buildings for non-continuous habitation such as lightly built free-time housing, warehouses and sheds, noise barriers, fence and other lightly loaded piers.

Demanding projects Basic buildings and structures, lighting and traffic control posts and portals.

Very demanding projects Complicated structures and buildings Bridges, hydraulic constructions, industrial constructions and similar engineering

structures. Columns and masts for electrification, power transmission and data transmission

networks. Structures subject to dynamic or otherwise exceptional loads, such as significant

horizontal loads, bending or high vertical loads, or ones subject to special requirements.

dst

dg

Mixture of soil and mortar

Drill rod

Grouted shaft

B/455/Pora./fig08

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2 STATUS OF INSTRUCTIONS

2.1 General These instructions are based on the laws, ordinances and regulations of the Finnish Building Code (RakMK), decisions of the Ministry of the Environment concerning Eurocodes and use of their national application documents as an alternative design system, and established European Standards (SFS-EN). The instructions for drilled piling are transitional and deal with the design, execution and quality control of drilled piles. An effort has been made to build the instructions on European Standards while taking into account Finnish soil conditions and piling practice. The user of these instructions must be aware of the current status of national guidelines and European Standards. Due to the incompleteness of the CEN Standards available at the time these instructions were prepared, there may be inconsistencies between said standards and the instructions. In case of any contradictions, Draft Standard CEN/TC 288 N213E Execution of special geotechnical work. Micropiles (April 2000) takes precedence.

2.2 Rules, regulations and standards for design The alternative design systems consist of a system based o the Finnish Building Code and the Foundation Engineering Instructions (RIL-121, 1988) and a system based on Eurocodes and their national application documents (NADs). So far, the use of Eurocodes in bridge design has not been approved. The following is a list of Eurocode-based standards published by the Finnish Standards Association and the corresponding application documents published by the Ministry of the Environment SFS-ENV 1991-1:1995

Eurocode 1: Basis of design and actions on structures Part 1: Basis of design

National application document for Prestandard SFS-ENV 1991-1:1995

Eurocode 1: Basis of design and actions on structures. Part 1: Basis of design

SFS-ENV 1992-1-1 Eurocode 2: Design of concrete structures Part 1: General rules and rules for buildings

National application document for Prestandard SFS-ENV 1992-1:1991 Eurocode 2: Design of concrete structures Part 1: General rules and rules for buildings

SFS-ENV 1993-1-1:1992 Eurocode 3: Design of steel structures Part 1: General rules and rules for buildings

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National application document for Prestandard SFS-ENV 1993-1-1:1992 Eurocode 3: Design of steel structures Part 1-1: General rules and rules for buildings

SFS-ENV 1993-5:1997 Eurocode 3: Design of steel structures Part 5: Piling

SFS- ENV 1994-1-1:1992 Eurocode 4: Design of composite steel and concrete structures Part 1: General rules and rules for buildings

National application document for Prestandard SFS-ENV 1994-1- 1:1992(NAD)

Eurocode 4: Design of composite steel and concrete structures. Part 1-1: General rules and rules for buildings

SFS-ENV 1997-1 Eurocode 7: Geotechnical design. Part 1: General rules

National application document for Prestandard SFS-ENV 1997-1

Eurocode 7: Geotechnical design. Part 1: General rules

SFS-ENV 1997-2

Eurocode 7: Geotechnical design. Part 2: Laboratory testing

SFS-ENV 1997-3 Eurocode 7: Geotechnical design. Part 3: Field testing

2.3 Standards This section lists all national (SFS) and European (SFS-EN) standards which are to be taken into account in the design and execution of piles. The rules and regulations of the effective version of a standard are to be followed. Listed are also prestandards and proposals for standards (SFS-ENV, ENVC and prEN) SFS-EN 996:1996

Piling equipment. Safety requirements SFS-EN 791:1996

Drill rigs Safety SFS-EN 1536:1999

Execution of special geotechnical work. Bored piles SFS-EN 1537:2000

Execution of special geotechnical work. Ground anchors SFS-EN 1538:2000

Execution of special geotechnical works. Diaphragm walls

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SFS 3165:1993

Cement. Composition, specification and conformity criteria. Part 1: Common cement

SFS-EN 12063:1999

Execution of special geotechnical work. Sheet-pile walls SFS 1215:1996-08-26

Reinforcing steels. Weldable hot rolled ribbed steel bars A500HW SFS 1257:1996-08-26

Reinforcing steels. Cold worked ribbed steel bars B500K SFS-EN 10025:1990

Hot rolled products of non-alloy structural steels. Technical delivery conditions

SFS-EN 10219-1:1998 ja SFS-EN 10219-2-1998

Cold formed welded structural hollow sections of non-alloy and fine grain steels. Part 1 Technical delivery requirements. Part 2 Tolerances, dimensions and sectional properties.

SFS-EN 287-1:1997 Approval testing of welders. Fusion welding. Part 1: Steels

SFS-EN 25817:1993

Arc-welded joints in steel. Guidance on quality levels for imperfections (ISO 5817:1992)

SFS-EN 449:1995

Welding consumables. Covered electrodes for manual metal arc welding of non alloy and fine grain steels. Classification.

SFS-EN 29692:1994 Metal-arc welding with covered electrode, gas-shielded metal-arc welding and gas welding. Joint preparations for steel (ISO9692:1992)

SFS-EN 288-1:1997, SFS-EN 288-2:1997, SFS-EN 288-3:1998

Specification and qualification for welding procedures for metallic materials; Part 1: General rules for fusion welding. Part 2: Welding procedure specification for arc welding. Part 3: Welding procedure tests for the arc welding of steels.

Here follows a list of European Prestandards (SFS-ENV or ENV) and European Draft Standards (prEN) under preparation: SFS-ENV 206

Concrete. Performance, production, placing and compliance criteria.

15/68 SFS-ENV 197-1

Cement Composition, specifications and conformity criteria. Part 1: common cements

ENV 10080

Steel for reinforcement of concrete, weldable ribbed reinforcing steel B500 Technical delivery conditions for bars, coils and welded fabric.

EN 12699:2000

Execution of special geotechnical work. Displacement piles

EN 12715:2000 Execution of special geotechnical work. Grouting

prEN 1008:1997

Mixing water for cement Specifications for sampling, testing and assessing the suitability of water, including wash water from recycling installations in the concrete industry as mixing water for concrete

prEN 1260:1996 Aggregates for concrete including those for use in roads and pavements

CEN/TC 288 N213E Execution of special geotechnical work. Micropiles

(April 2000) (under preparation)

2.4 National standards and regulations In this section are listed all national standards to be taken into account in the design and execution of the piles referred to in the instructions. Finnish Building Code (RakMK)

B3 Foundation structures B4 Concrete structures B7 Steel structures

The instructions are complemented, for instance, by the effective sections of the following publications which deal with piling issues. Instructions on the programming and execution of ground investigation: Ground investigation instructions for building construction (SGY, TPO-83, 1983) Instructions for geotechnical laboratory work (SGY, GLO-85, 1985) Sounding manuals (SGY) Sounding manual Iweight sounding and dynamic probing (1980) Sounding manual IIvane test (1999) Sounding manual IIIsampling (1984) Sounding manual IVmonitoring of groundwater level (1990) Sounding manual Vdrilling (1986)

16/68 Rock investigation instructions for construction (SGY, RKO-79, 1979) Instructions for the design and construction of foundation structures: Foundation engineering instructions 1988 (RIL 121-181) Structural loading instructions (RIL 144-1987) High-capacity piling instructions SPO-2001 (SGY, RIL-212-2001) Building excavation instructions (RIL 181-1989) Tasks of geotechnical design GEO 95 (SKOL 1995) General building specifications (RYL-90, 1989) Talo 90 (Building 90) nomenclature (The Finnish Building Centre Ltd) Instructions concerning design of composite piles Composite structures, design instructions (TRY, BY 26, 1988) Application instructions for composite structures (TRY, BY 36, 1991) Instructions for supervision: Instructions for the supervision of foundation engineering works (SGY PRP-84, 1984) Abbreviations: BY, Suomen Betoniyhdistys ry. (Concrete Association of Finland) RIL, Suomen Rakennusinsinrien Liitto ry.(Association of Finnish Civil Engineers) SGY, Suomen Geoteknillinen yhdistys ry. (Finnish Geotechnical Society) TRY, Suomen Tersrakenneyhdistys ry. (Finnish Constructional Steelwork Association) VTT, Valtion teknillinen tutkimuskeskus (Technical Research Centre of Finland)

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3 DEFINITIONS Centralizer Spacers attached to reinforcement which centre reinforcement cage and prevent it from pressing

against the casing. Cohesion pile Pile that transmits the load to soil layers via adhesion acting on pile shaft. Compression pile Pile that takes compression forces parallel to its longitudinal axis. Concreting pipe

Metal pipe for concreting with a funnel and a chute. Cut-off level

Level of pile head after removal of excess length Deviation in pile inclination Difference between intended and actual inclination of pile at cut-off level. Deviation in pile position Difference between intended and actual position of pile at cut-off level. Drill rod

A hollow rod that transmits the blows of a top hammer and the power that rotates the bit, and conveys the medium that operates the DTH hammer and the flushing agent for the drill bit. The hollow drill rod sits inside the casing. Some top hammer hammers may also use a solid drill rod.

End-bearing pile A pile which transfers most of the load via the tip to the rock or soil layer.

Foundation pile Pile that functions as a foundation or a foundation component. Friction pile A pile that transmits most of the load to soil layers via the friction on pile shaft. Geotechnical capacity Capacity of soil or rock to bear loads transmitted through pile.

Geotechnical diameter, dg Pile diameter used in geotechnical dimensioning of pile and width of soil layer supporting pile in

dimensioning of buckling. Grout Mixture of cement or different chemicals and water that is forced into pores of surrounding soil or

cracks in rock under pressure. Head of pile

Upper end of pile.

18/68 Horizontally loaded pile Pile subject to significant horizontal loads. Inclined pile

A pile installed off the vertical. Lightweight sound

A device intended for inspections inside the casing made of closed, lightweight pipes. Its weight corresponds approximately to the buoyancy exerted on it.

Loading test at constant speed A static loading test where a pile is compressed into the soil at constant speed while constantly

monitoring the compressive force. Mortar Concrete of extremely small aggregate size which can form a composite structure with a steel

pipe but does not penetrate into soil. Negative shaft resistance Load on pile created by the friction and adhesion forces between pile shaft and the surrounding

soil layer, when the soil settles more than the pile. Pile Slender structural component which transmits loads to rock of a bearing soil layers and prevents

displacement of structures. Pile base Bottom of drill hole. Pile casing A drill pipe that can be left in the ground or withdrawn; it may function as a bearing structure of

the pile by itself or as part of a composite structure. If left in the ground, it can ensure successful concreting.

Pile section A pile shaft, or part of one, made prior to drilling or installing a pile. Pile shaft Bearing structure of pile, part between head and tip of pile. Preliminary pile Pile made prior to piling proper intended to ensure suitability of chosen pile type for the site. Reinforcement cage The reinforcement cage consists of main bars parallel with the pile shaft tied together with spiral

stirrups. Rock contact Contact between pile base and rock. Shaft diameter, d Maximum pile diameter between head and tip of pile.

a) external diameter of casing with piles drilled using a casing

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b) diameter of drill bit with piles drilled without a casing Shaft resistance Friction and/or adhesion acting on skin of shaft. Skin of pile Contact surface between pile shaft and soil. Stabilizing fluid A mixture of water and bentonite or other suitable materials. Used sometimes in Finland to

prevent hydraulic failure of bottom of drill hole. Static loading test A loading test where a pile is subjected to an axial and/or lateral load in order to determine its

load/displacement correlation and/or failure and/or yield capacity. Stepped loading test A static loading test where loading of a pile is increased in steps holding each load constant for a

certain time. Loading is, however, maintained at least long enough to reach a pile penetration rate smaller than the set limit.

Structural capacity Capacity of pile shaft to transmit received loads to the ground or rock. Structural diameter, dst Pile diameter used for structural dimensioning of pile. Suspension bars Steel bars from which the reinforcement cage in the casing or the drill hole is suspended. Target level Level to which tip must be drilled in order that the pile obtains sufficient geotechnical capacity. It

must be sufficiently below the planned excavation or cutting level. Tension pile A pile that takes tensile loads parallel to its longitudinal axis. Test pile

Pile loaded to determine bearing capacity of pile and dependence of settlement on loading in the examined soil layers.

Tip of pile Lower end of pile. Tremie for underwater concreting Concreting pipe equipped with watertight joints and a watertight plug, which opens when

underwater concreting is started. During concreting the lower end of the tremie pipe is submerged in the fresh concrete.

Trial pile Pile made before piling intended to ensure the applicability of the piling method to a certain site.

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4 REQUIRED PILING DOCUMENTATION

4.1 Documentation required for regular piling This chapter deals with the documentation required for regular piling work based on the European Prestandard CEN/TC 288 N213E Execution of special geotechnical work. Micropiles (April 2000) which is under preparation. All information essential to drilled piling must be included in the construction documents. The following information essential for piling must be available for use on site in written form prior to the launching of works in demanding and very demanding projects: Construction documents: contract specifications, work specification or quality requirements and

related ground investigations, foundation engineering and structural drawings. The requirements concerning ground investigation are presented in Chapter 5.

Work schedule and quality plan which describe the piling method in detail, the piling sequence and quality control measurements, inspections and testing.

Site conditions such as its boundaries, inclination of ground surface, access to area, factors restricting work, etc.

Location and condition of nearby buildings, roads, railways, equipment, lines and cables, underground structures, foundations, piles, anchors and other obstacles in the ground, archaeological relics and structures that hamper work such as power lines and electrical and lighting systems.

Data on soil contamination and factors that induce corrosion and other similar drawbacks which may impact the selection of pile type or work safety.

Threshold values for environmental nuisances such as noise, vibration and emissions as well as other statutory constraints such as time limits for construction works.

Information on piling, other substructure construction or underground works done on the site or nearby earlier.

Simultaneously ongoing activities which may have an impact on the work such as a nearby excavation or lowering of the groundwater level.

Location of bench marks. Allowable deformations in adjacent buildings and structures. Required control measurement system and inspections. Dimensions of usable traffic routes and working areas.

4.2 Further documentation required for foundation strengthening The following data is also necessary for foundation strengthening: Allowable deformations in buildings to be strengthened and adjacent buildings Condition of buildings to be strengthened and adjacent buildings as well of their foundations Dimensions and materials of existing foundation structures, floors, drains, drainage and

groundwater control systems Dimensions of usable spaces.

21/68 5 GROUND INVESTIGATIONS

5.1 Requirements The conduct of ground investigations is regulated on the general level by national codes (RakMK B3 Pohjarakennus) and effective national guidelines and European Standards (ENV 1997-1, ENV 1997-2, ENV 1997-3). Ground investigation techniques, spacing of test points and sounding depth are chosen on the basis of the requirements of the piling project and the pile-bearing layer. A target level, pile diameter and piling equipment are determined on the basis of the ground investigation. That is why a ground investigation is essential also in small piling projects. Table 1 shows the used ground investigation techniques according to the requirements of the piling project and type of pile support. The following chapters describe in more detail the carrying out of ground investigations and the numbers of sounding and sampling points done. Table 1 Ground investigation methods according to requirements of piling project and type of pile

support.

percussion drilling

EASY SITES Piles bearing on rock (X) Piles bearing on ground (X) Horizontally loaded piles (X) DEMANDING SITES Piles bearing on rock X (X) X (X) Piles bearing on ground X X (X) Horizontally loaded piles X X (X) X VERY DEMANDING SITES X Piles bearing on rock X X (X) (X) Piles bearing on ground X X (X) X Horizontally loaded piles (X) (X) X X x required (x) when necessary

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5.2 Easy sites

5.2.1 Piles bearing on rock Percussion drilling should be performed to aid the design of drilled pilling (Kairausopas V 1986) at each corner of the planned building or at individual structures or at every fourth noise barrier or fence pier or at maximum intervals of 20 m. In exceptional cases drilled piling may be equated with ground investigation. Then, pile drilling must be documented in the same manner as percussion drilling (Kairausopas V 1986). The technique may be used to estimate pile length.

5.2.2 Piles bearing on ground Ground investigations for the design of drilled piling may be performed as weight soundings which should be done at least at each corner of the planned building or at individual structures or at every fourth noise barrier of fence pier or at maximum intervals of 20 m.

5.2.3. Horizontally loaded piles It is recommendable to perform weight soundings for pile dimensioning at least at each individual structure or at every fourth noise barrier or fence pier or at maximum intervals of 20 m.

5.3 Demanding sites

5.3.1 Piles bearing on rock At least percussion drillings must be done for the design of drilled piling. Dynamic probings should also be implemented in order to determine the drillability of soil layers. Drillings must be performed at least at the corners of a planned structure. Depending on the extent of the variations in the rock surface and soil conditions, the drilling points should be spaced at maximum intervals of 5-15 m. Percussion drillings must extend 3 m into the rock and 2 m below the target level for the pile tip. The definition of the parameters needed in calculating the buckling load of a pile requires performing vane tests in soft organic or fine-grained soil layers. Moreover, disturbed samples should be taken from every fourth drilled point in order to determine soil-layer boundaries.

5.3.2 Piles bearing on ground Dynamic probings must be performed at least at the corners of the designed structure. Depending on the extent of the variations in the rock surface and soil conditions, the test points should be spaced at 5-15 m intervals (max). When the piles are supported by soil layers, drillings should extend at least 3 m below the target level for piles.

23/68 The definition of the parameters needed in calculating the buckling load of a pile requires performing vane tests in soft organic or fine-grained soil layers. Moreover, disturbed samples should be taken from every fourth boring point in order to determine soil-layer boundaries.

5.3.3 Horizontally loaded piles Horizontally loaded drilled piles require a weight sounding or a cone penetration test at least at every other barrier or fence pier, or at each individual pier, or at least at 15 m intervals. In order to determine soil-layer boundaries, disturbed samples must be taken at every other sounding point. To secure horizontal capacity, vane tests must be performed at every fourth pile in organic and fine-grained soil layers.

5.4 Very demanding sites

5.4.1 General At very demanding sites a ground investigation must be made at each foundation and at each corner of a large foundation such as pile group foundations of bridges. Moreover, the requirements of the client must also be met in the programming and implementation of ground investigations in case they are stricter than the ones presented here.

5.4.2 Piles bearing on rock The position of the rock face is always determined by percussion drillings. The position and forms of the rock face must always be determined when the piles are to penetrate into the rock. In the case of large-diameter drilled piles (d > 300 mm), a percussion drilling is required at each pile. The drilling must penetrate 3 m into solid rock and at least 2 m below the target level for pile tips. The properties of all soil layers above the rock must be determined. Soil-layer boundaries are determined by taking a sufficient number of disturbed soil samples. The strength of coarse-grained and moraine layers can be determined indirectly on the basis of soil type and sounding resistance. The drillability of soil layers can be predicted by dynamic probings. The definition of the parameters needed in dimensioning the buckling load of a pile requires vane tests in soft organic or fine-grained soil layers. In the case of fine-grained and organic soil layers, soil samples should be taken in order to determine compressibility and/or strength by an oedometer and/or triaxial tests.

5.4.3 Piles bearing on ground Ground investigations are conducted by dynamic probings. The soundings must extend at least 3 m below the target level for piles. The properties of all soil layers above the rock must be determined. Soil-layer boundaries are determined by taking a sufficient number of disturbed soil samples.

24/68 The stability of coarse-grained and moraine layers can be determined indirectly on the basis of soil type and sounding resistance. The drillability of soil layers can be evaluated by dynamic probings. The definition of the parameters needed in dimensioning the buckling load of a pile requires performing vane tests in soft organic or fine-grained soil layers. In the case of fine-grained and organic soil layers, soil samples should be taken in order to determine compressibility and/or strength by an oedometer and/or triaxial tests.

5.4.4 Horizontally loaded piles When making use of the lateral capacity of a pile, for instance, with horizontally loaded or bending stressed piles, especially the strength and deformation characteristics of the soil layers supporting the top part of the pile must be determined. Strength values of fine-grained soil layers can be determined by vane tests. Strength of coarse-grained and moraine layers can be determined indirectly on the basis of soil type and sounding resistance. If horizontal loads and moment stresses are heavy, soil samples need to be taken in order to determine compressibility and/or strength by an oedometer and/or triaxial tests. The groundwater level is monitored and the range of variation is estimated.

5.5 Presentation of ground investigations The issues raised in the Foundation engineering instructions (RIL 121-1988) as well as the clients requirements must be considered in the presentation of ground investigations. Ground investigation drawings, maps and printouts as well as the description of soil conditions must show all soil layers and factors essential to drilled piling, including: a) Ground level at all examined points based on some known elevation-measurement system. b) Locations and properties of soil layers that are soft, loose or easily disturbed by piling, unstable, or

tend to compact. c) Thickness, ingredients and other properties of fill layers. d) Rocks, boulders and built underground obstacles which impact piling or require special measures

or tools to penetrate or remove. e) Properties of soft layers beneath coarse-grained layer which affect performance of pile foundation. f) Levels of perched groundwater and actual groundwater including range of variation as well as data

on artesian water. g) Depth and inclination of rock face. h) An account of the aggressiveness of soil or groundwater which may affect the durability of pile

materials in contaminated or otherwise high-risk land areas. It is recommendable to present the ground investigation as part of the work specification, so that the description of soil conditions which deals with geotechnical soil layers and their properties by layers from the surface to the rock, and which makes reference to the ground investigation drawings and laboratory test results constitutes the first chapter of the work specification.

25/68

6 PILE MATERIALS AND REINFORCEMENTS

6.1 General All materials and reinforcements used to make drilled piles must meet the requirements of the Finnish Building Code (RakMK) and SFS-EN Standards. The supplier of a material cannot be changed without prior approval. Any rejected material must be removed immediately from the site.

6.2 Ingredients of concrete, mortar and grouts

6.2.1 Cement and substitute additives Concrete must be made with construction cements that conform to Standard SFS 3165. Other cement types may also be used if their composition has been analyzed in detail and their behaviour under similar conditions has been established. Aluminate cement must not be used in making concrete. Other additives may be used instead of cement as a binder on the condition that it can be shown that they have a beneficial impact on the workability of concrete, heat generation during the curing of concrete as well as the attainment of concrete qualities corresponding to the ambient conditions. When using as binder substances from which no experience has been gathered under similar conditions, workability must be ensured through preliminary tests. If substitute binders are used, concrete quality is to be assessed based on the water-binder ratio instead of the water-cement ratio. When making frost resistant concrete using an air-entraining agent, fly ash may be added to the concrete only when using Portland cement. Then, the fly ash must be of grade A and its maximum content 25 percent of the amount of Portland cement (RakMK B4).

6.2.2 Aggregate Used aggregates must comply with the requirements of Betonin kiviainesohjeet By 43 (1996). The material extraction site and grade and particle-size distribution of the aggregate must be approved prior to launching the work. Rounded aggregate is recommended when using a concreting pipe Aggregates are to be clean and must not contain organic or otherwise detrimental substances. The maximum size of aggregate is 32 mm or 1/4 of the clear distance between main rebars or 1/6 of the inside diameter of the concreting pipe, whichever is smaller. Aggregates of different types and particle size must be stored separately.

26/68 Frozen aggregate must be heated so that it contains no ice or frost.

6.2.3 Water If the water for making the concrete is not drawn from a water distribution network, the quality of the water must be examined and be approved by the client.

6.2.4 Admixtures Admixtures must meet the requirements of the Finnish Building Code (RakMK B4) and certified product declarations must be available. The following admixtures which impact concreting may be used: plasticizers that reduce the amount of water needed and increase plasticity retardants air-entraining agents Admixtures must not contain harmful ingredients which degrade the durability of concrete or cause rebars to corrode. If several admixtures are used, their combined effect must be determined. Use of chloride-laden admixtures is forbidden. Admixtures may be used for the following purposes to ensure the strength, durability and placement properties of concrete: to improve workability of fresh concrete to reduce water-content of concrete, and to render the mix more plastic in order to prevent

separation and honeycombing after placement to retard hardening of concrete during placement and possible interruptions in placement to improve durability of concrete. The concrete may become defective if unsuitable admixtures are used. The mixing ratios of admixtures must be approved by the client prior to concrete placement. The admixtures may be mixed into the concrete during the making of concrete or prior to placement. Air-entraining agents may be added to the concrete mix used for the top sections of piles exposed to frost.

6.3 Concrete

6.3.1 General The proportioning of concrete used for large-diameter piles must be designed in accordance with the Finnish Building Code (RakMK B4) taking into account the requirements of Table 2. The design strength of concrete used for drilled piles must be at least K30, and maximum strength values of K50 may be used in dimensioning. The amount of binder in the concrete, considering the durability properties of the plan, must be in accordance with Table 2. Plasticity must be in line with Table 3.

27/68 The concrete mix used for a pile must: have high durability against separation have high plasticity and cohesion have good pourability be self-compacting be sufficiently workable during pouring until the casing is withdrawn. Table 2. Mix proportions of concrete Amount of binder - dry placement 325 kg/m3 - underwater placement 375 kg/m3 Water-cement ratio (W/C)

< 0.6

Fines content (d < 0.125 mm) including binder - aggregate d > 8 mm 400 kg/m3 - aggregate d 8 mm 450 kg/m3 Table 3. Consistency grading of concrete mix Spread test; range of concrete cake diameter () [mm]

Slump test; range of settlement (H) [mm]

Concreting conditions

460-530

130-180

Dry concreting

530-600

160 Underwater concreting or concreting by pumping

570-630

180 Underwater concreting with stabilizing fluid using a tremie.

Measured diameter or settlement is rounded to nearest 10 mm. If the amount of binder from Table 2 and the consistency of Table 3 do not produce proper compaction of the mix, the amount of binder and consistency grade may be altered on approval of the client. Sufficient protection against the effects of soil and/or groundwater must be ensured either through proportioning or by leaving the casing in the ground. In aggressive groundwater or soil conditions sufficient protection is not necessarily attained by mere proportioning. Contaminated soil or water can degrade the quality of the concrete mix. Heavy metals may retard the hardening of concrete or change its pore structure. Unhardened concrete may be protected against groundwater flow by a permanent casing or a permanent lining.

6.3.2 Mixing of ingredients The general requirements set for mixing and ingredients must conform to the rules of the Finnish Building Code (RakMK B4) and the figures presented in the design documents.

28/68 Ready-mixed concrete is to be used to concrete drilled piles. Unless the designs indicate otherwise, three separate batches of concrete must be made as a preliminary test. Six (6) test cubes or cylinders are to be made of each test batch of concrete. Two (2) are to be compressed of 7-day old concrete, two (2) of 28-day old concrete and another two (2) are to be stored away for possible further examination. Water must not be added to the concrete mix immediately before placement until proper mixing of the admixtures has been secured. The water-cement ratio indicated in the designs must be maintained.

6.3.3 Compliance verification of concrete The compliance of concrete must be verified in accordance with Section B4 of the Finnish Building Code (RakMK) for constructions where the load-bearing structure is of concrete. When concrete is delivered by a ready-mixed plant with non-certified quality control, the following conditions must also be met: The making of test pieces from fresh concrete for compressive strength tests on site must carried out as follows: a test piece is to be made for the first three piles, and a test piece for every subsequent five piles, and if the concrete volume of an individual pile < 4 m3,

one test piece for every subsequent fifteen (15) piles two extra test pieces after long interruptions in placement (over 7 days) a sample for every 75 m3 of concrete placed in a single day at least one test piece for each pile if the concrete strength requirement is over K45. A complete record must be kept of the results of the compliance tests of concrete. The results of the tests must also be entered in the concreting record.

6.4 Mortars The size of mortar aggregate must not exceed the following values: d85 4 mm d100 8 mm Mortar strength must be at least K25. If mortar is used as a bearing structure, the value must be at least K30. The maximum strength value that can be considered in dimensioning is K60. The maximum allowed water-cement ratio is 0.6. The guidelines of Chapter 6.3.3 and Section 6.3.8 of the Finnish Building Code (RakMK B4) are to be followed in verifying compliance.

29/68 6.5. Grouts

6.5.1 General Cement-based grouts are to comply with the instructions of this chapter. The properties of other grout types are dealt with in more detail in Draft Standard CEN/TC 288 N213E Execution of special geotechnical work. Micropiles (April 2000). Grouts must be cement grouts or other substances that conform to the design. Cement-based grouting mortars are mixtures of cement and water. If the maximum size of aggregate is 2 mm and its portion by weight is less than that of cement, the substance is considered a grout otherwise it is regarded as a mortar. The water-cement ratio must be suited to the actual soil conditions. Yet, it must not exceed 0.55. The strength of a grout must be at least K25. A grout cannot be used as a bearing structure. Separation after two hours must be less than 3 percent. When using a grout as protection against corrosion, its separation and shrinkage must be taken into account in proportioning.

6.5.2 Determination of compliance At least two series of three test pieces must be made at each site at seven day intervals for testing compressive strength. In automatic mixing, batching is to be checked regularly. If using non-automatic mixing, the mixing ratios must be recorded.

6.6 Other substances used in drilling Liquids used to stabilize drill holes: bentonite slurry polymers other liquids. The required properties of liquids reinforcing a drill hole are dealt with in Standard SFS-EN 1536, section 6.5. The liquids and admixtures used in drilling must not have detrimental effects on steel, mortar or the properties of the surrounding soil, the environment or groundwater.

6.7 Steels

6.7.1 General The reinforcement steels, steel pipes or steel sections used as pile reinforcement must meet the conditions set in national product standards, e.g. SFS 1215 (A500HW) and SFS 1257 (B500K), as well as European product standards, e.g. SFS-EN 10025 and SFS-EN 10219.

30/68 Centralizers must be installed on pile reinforcement at intervals not exceeding 2 metres.

6.7.2 Reinforcement steels In the selection of steel grade attention must be paid to the assembly and weldability of cage reinforcement. Reinforcement steel joints must be such that they do not decrease reinforcement capacity, and they must conform to the Finnish Building Code, B4 Concrete structures.

6.7.3 Structural sections Whenever piles are reinforced with steel pipes or sections, the reinforcement must be designed in accordance with ENV 1994-1-1. Weldability must be considered in the selection of steel grade where necessary.

6.8 Joints

6.8.1 General Direction of pile may change at a joint by a maximum of 1:100 in the easy category, 1:150 in the demanding category, and 1:200 in the very demanding category. If piles are jointed so that the joints withstand at least the same tensile, compressive and bending action as the pile section, pile capacity need not be decreased due to joints. If the properties of the joint are inferior to those of the pile section, it must be considered in the dimensioning of the pile. The strength and deformation properties given by the pile-joint manufacturer may generally be used in dimensioning. Joints must be protected against corrosion just like the actual pile element. Piles may be extended by welding or using mechanical joints. The material of the joints must be composed of materials that do not essentially increase the risk of corrosion. Grouted pile sections are generally extended using external threaded sleeves.

6.8.2 Extension of piles by welding The details of welded joints must be shown in site plans. Welding of joints is explained in the work and quality plan for the site. The details of the inspection procedure for welded joints during piling are agreed separately in each case. When using solid-bar reinforcement, the joint surfaces must be machined in a mechanical workshop. The planarity of the joint surfaces must be < 0.1 mm.

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Fig. 9. Example of welding design for solid bar. Weld quality requirements for joints are presented in Table 4. Table 4. Weld quality requirements for bearing steel components of drilled piles for different

requirement categories. SFS-EN 25817

Requirement category of site Weld quality class Weld-quality requirement very demanding B demanding

demanding C good easy D satisfactory

In the easy category joints are inspected visually to determine weld dimensions, misalignments, undercuts and possible welding defects extending to the surface. Ultrasonic examination (NDT) of welds is done only after they have passed visual inspection. In the case of the demanding category, the welder is to do a so-called production weld test prior to welding. All seams are also to be inspected visually. The production weld test involves welding two pile pipes together in accordance with the welding program under conditions comparable to the installation conditions. Welding length is about a quarter of the entire weld. A piece about 100 mm square, which contains a weld, is cut from a spot that appears critical in visual inspection. One cross-sectional surface is ground and inspected visually. It must meet the requirements of the applicable weld class as to detectable defects. Special attention must be paid to complete penetration. The execution of a production weld test is recorded in the documents of the site in question. The test is valid for a maximum of 2 months when the test has been conducted under similar conditions using similar pile materials and types. At very demanding sites, at least 10 percent of the seams are inspected ultrasonically in addition to performing the production weld test and visual inspection. In ultrasonic examination an entire weld is inspected, that is, one weld out of ten is examined entirely unless otherwise agreed. However, at least 30 percent of the seams of solid rods must be inspected ultrasonically. Inspections are documented by seams in the inspection record. Inspection must always start with the first weld involving, for instance, examination of internal weld defects such as incomplete fusion, pores and slag inclusions as well as defects of the root of the weld such as incomplete penetration and too large root ridge. Defects in excess of the limits of the weld category are repaired. Repaired welds as well as two other welds are reexamined. An NDT examination may be conducted only by a qualified inspector. A related inspection record is always prepared.

15

A/455/01/PORAPRAK

100

60 V groove (60)

0,1

32/68 7 DESIGN

7.1 General The design of drilled piles must apply an engineering system based on the provisions of the Finnish Building Code and Foundation Engineering Instructions (RIL 121, 1988) or on Eurocodes and their National Application Documents (NAD). The instructions to be observed in design and dimensioning are listed under 2.2. and 2.3. The design must be based on special requirements for the project, presented in Chapter 4 ground investigations, presented in Chapter 5 requirements for pile material presented in Chapter 6 Permissible deviations in positions and inclination of piles, and requirements for the piling work must be taken into account in the design, as shown in Chapters 7.6 and 8.

7.2 Tasks included in the design The following tasks are included in the design: collection and assessment of basic data programming of ground investigation geotechnical and structural dimensioning of piles effect of drilling on surrounding soil and, through it, on surrounding structures design and supervision of test piling, and evaluation of results, where needed piling design, which contains

work specification or quality requirements containing instructions or requirements for drilling, cleaning of drill hole, reinforcement and concreting

measurements to monitor the effects of the piling work on adjoining buildings and/or the building to be strengthened, with permissible limits

quality control tests for piling requirements for the piling records requirements for the as-built drawings

piling drawing that includes pile loads and numbering of piles target level of piles, which must be at least 3 metres below the future excavation or cutting

level permissible deviations of dimensions and locations piling sequence

7.3 Limit states and dimensioning mechanisms to be considered The compression and lateral capacity of piles, and tensile capacity, where applicable, must be checked in both service and ultimate limit states. Limit states possibly caused by the displacement of piles in the foundation structures or structures supported by them must be checked both in service and ultimate limit state.

33/68 Loads on piles in the ultimate limit state must be multiplied by the partial safety factors of the load corresponding to the loading situation, and the pile capacity must be divided by the partial safety factor of capacity. Pile analyses in serviceability limit state must be based on the characteristic values of loads on the piles, thus pile capacities are to be calculated according to the characteristic values of capacity. At least the following dimensioning mechanisms must be taken into account in the dimensioning of the pile foundation: settlement heave lateral movement differential settlements and distortions soil-structure interaction capacity of foundation and/or single pile against compression, tension, bending and lateral load overall stability dynamic stiffness, where applicable stability of drill hole during concreting, and need of casing Dimensioning situations must be inspected in all limit states on the basis of determining loads and load combinations.

7.4 Geotechnical design of piles

7.4.1 General The transmittance of vertical load to rock or ground, or the ratio of shaft resistance to point resistance, depends on the piling method, pile dimensions and materials, and soil conditions as well as the resistance-deformation behaviour of soil and the loading time. Lateral loads on the pile foundation can be transmitted to soil layers by the lateral resistance of soil and/or by inclined piles. This document presents the principles of geotechnical and structural design of piles bearing on rock. Geotechnical dimensioning of piles bearing on ground and the dimensioning of the lateral resistance of the pile are to be carried out according to the High-capacity piling instructions (SPO-2001). However, this document contains some additions to the High-capacity piling instructions. Dimensioning of the geotechnical compression, horizontal and tensile capacity of piles should be based on the safety level defined in ENV 1997-1 and the related national application document (NAD), with regard to the additions presented here and the partial safety factors of load combination C defined in ENV 1991-1.

7.4.2 Calculation of geotechnical bearing capacity In the dimensioning of the base and shaft resistance of piles, the drilled pile is usually treated as a replacement pile. Pressure grouting may cause soil displacement, which can be taken into account in the geotechnical dimensioning of piles and based on data derived from load tests under similar conditions. The geotechnical bearing capacity of the pile should be determined by dimensioning separately the contribution of the base and the shaft to the geotechnical bearing capacity.

34/68 It is not always necessary to take the shaft resistance into account; this is particularly true of piles bearing on rock. Rock faults and cracks should be taken into account in dimensioning, where applicable. Geotechnical dimensioning of drilled piles should be verified primarily with the following methods: earlier static loading tests under similar conditions with a corresponding pile type static loading tests

7.4.3 Base resistance of piles bearing on rock The pile tip can be presumed to be bearing on rock, if observations during drilling and the ground investigations indicate that the tip of the pile has reached solid rock. The base resistance of a drilled pile bearing on solid rock can be dimensioned for service state loads based on yield strength of the pile, if rock contact is verified by percussion drilling and observations during drilling. The uniaxial compressive strength of hard and solid Finnish intrusive rock is generally in the range of 200-300 MPa. Piles are to be drilled at least 3 d deep but not less than 0.5 m and not more than 1.5 m into solid rock. However, piles must always be drilled at least 3 m below the future excavation or cutting level. This ensures sufficient bearing capacity of the pile tip in relation to the structural bearing capacity of a steel or composite pile, and slipping of the pile tip on the rock is prevented. If the levels of the tips of adjacent piles differ considerably, shorter piles must go deeper. If the rock face is very steep, additional drillings around the piles may be necessary. In rock with faults, piles can be drilled deeper or shaft-grouted piles used.

7.4.4 Shaft resistance of piles bearing on rock Where piles are supported on the plane of weakness of rock or are under tensile stress, it may be necessary to factor shaft resistance of the pile in rock into dimensioning. If the shaft resistance of a pile bearing on rock is used, the casing is drilled to the surface of the rock, after which drilling is continued in rock. If the drilling method allows grouting of the casing simultaneously with the drilling of the pile section, rock drilling is not needed. The dimensioning strength of the adhesion between the concrete and the drill hole is usually presumed to be constant throughout the adhesion length. Then, the dimensioning value of the adhesion capacity is obtained from the formula:

Rsd = dLibd (1)

d is the outer diameter of drill bit Li is adhesion length bd is the dimensioning strength of adhesion, obtained from Table 5

35/68 Table 5. Dimensioning strength of adhesion between concrete and rock in solid rock.

Concrete tbd [Mpa] K30 0.75 K35 0.85 K40 0.95 K45 1.05 K50 1.10 K60 1.15

Adhesion between concrete or mortar and anchor steel is calculated in the same way as the adhesion capacity between concrete and the drill hole. The value of the adhesion strength between concrete and steel can be calculated according to RakMk B4 with the formula: bd = kbfctd (2)

kb is 2,4 for ribbed bars and 1.0 for round bars fctd is dimensioning value of the tensile strength of concrete or mortar

The adhesion between grouts, mortar and the drill rod of grouted drilled piles varies considerably depending on the pile profile. Where mortar or grout is used, the strength properties of the materials must be taken into account.

7.4.5 Bearing capacity of pile bearing on ground The load-bearing capacity of a pile bearing on ground is calculated according to the High-capacity piling instructions (SPO-2001). The effect of soil displacement caused by pressure grouting can be taken into account by a shaft resistance factor between the factors of a displacement and a non-displacement pile.

7.4.6 Tensile capacity of pile If a pile is subjected to permanent tensile stress, it acts as an anchor and must be designed according to the instructions on anchoring. The geotechnical tensile capacity of a pile is the sum of pile weight and the effective shaft resistance in tension. In the case of fine-grained soil layers shaft resistance cannot be exploited in long-term tension. The stress state around a tension pile differs from that around a compression pile, which means that the shaft resistance of a tension pile in soil is lower than that of a compression pile. An approximation for the characteristic value of the shaft resistance of a tension pile can be derived from the characteristic value of the shaft resistance of a compression pile as follows:

short-term loading R= Rsk (3) 1.6

36/68

long-term loading R=Rsk (4) 2.0

The tensile capacity of a pile in rock is the sum of pile weight and the shaft resistance of the casing grouted into the rock. The minimum anchoring length in rock of a pile under tension can be calculated according to the principle presented in Figure 10 using the formula:

(5)

Rtd is the dimensioning value of tensile stress d is the dimensioning unit weight of rock, generally 26.5 kN/m3 is generally 45

If the cracking of the rock has not been determined reliably, a minimum anchoring length of 3 m should always be used for tension piles. When dimensioning the tensile capacity of several adjacent piles, the effective weight of the rock cone on which the tension of the pile group is concentrated should be taken into account according to the principle shown in Figure 10.

Figure 10. Minimum anchoring length of a tension pile in rock.

L min

B/455/Pora./fig09

37/68 On the basis of tensile loading tests, the characteristic value of the shaft resistance of a pile is determined according to ENV 1997-1 and its national application document (NAD) complemented with the additions presented in Chapter 7.3.21. In the demanding category, the tension capacities of piles can be dimensioned on the basis of ground investigation results. In the very demanding category, where tensile loads are frequently repeated or cyclical, tensile resistance should be assessed by loading tests corresponding to the actual loading of the tension pile.

7.4.7 Lateral capacity of pile The lateral capacity of a pile should be dimensioned according to the instructions given in the High-capacity piling instructions (SPO-2001). The dimensioning of lateral capacity in the very demanding category should be based on numerical methods whose validity has been proven by loading tests simulating the actual loading of the pile or by results of measurements or loading tests conducted under corresponding conditions. Loading tests simulating the actual loading of piles must be performed when dimensioning a pile foundation in the very demanding category where no previous loading test results or practical experiences from a corresponding structure are available. When calculating lateral capacities of piles, soil strength parametres must be divided by the partial safety factors, and in the calculation of lateral loading they must be multiplied by the partial safety factors.

7.4.8 Dimensioning for a cyclic load Drilled piles should be dimensioned for cyclic loads according to the instructions given in the High-capacity piling instructions (SPO-2001).

7.4.9. Determining geotechnical bearing capacity of pile by static loading tests In case of piles bearing on ground the geotechnical load-bearing capacity can be determined by static loading tests according to the High-capacity piling instructions (SPO-2001). If pile diameter is (d

38/68 the partial safety factors of materials presented in European standards ENV 1992-1-1, ENV 1993-1-1, and ENV 1994-1-1, together with the partial safety factors of load combination B presented in ENV 1991-1. Piles bearing on rock can be dimensioned as piers, in which case the specific instructions pertaining to pile material or structural performance should be taken into account, such as the regulations presented in RakMk B7 for steel piles and the regulations presented in Liittorakenteet BY 26 and Liittorakenteiden sovellutusohjeet B 36 for composite piles. The interaction between the pile and soil may also be considered in the structural dimensioning of piles. In structural dimensioning, only the structural diameter can be taken into account. In buckling dimensioning, the geotechnical diameter can be used as the width of the soil layer supporting the pile. Stresses during the transport, handling and installation of piles should also be taken into account in the structural dimensioning of piles. A drilled pile should be designed in the same way as a steel structure, or a steel/concrete composite structure The structural class of concrete used in drilled piles and possible requirements for its durability must be presented in the designs, and they must meet at least the requirements presented in RakMk B4 or ENV 1992-1-1 and its national application document (NAD).

7.5.2. Corrosion of shaft-grouted piles When using external corrosion protection, the thickness of the protective layer must be at least equal to that presented in Table 6. In piles subjected to tensile or bending stresses, crack width in the service state must not exceed: 0.3 mm under non-aggressive conditions 0.15 mm under aggressive conditions The profile of the reinforcement should be taken into account in calculating crack width. Table 6. Minimum thickness of external corrosion protection layer in a non-aggressive

environment. Minimum thickness of protective layer [mm] Piles under compressive

action Piles under tensile or

bending action Grout 20 30 Mortar 35 40 Concrete 50 50 If the thickness of the protective layer used is smaller than that indicated in Table 6, corrosion is to be taken into account as a corrosion allowance for the steel cross-section, as shown in Table 7 in Chapter 7.5.3. In the case of drilled piles with a design service life of less than 20 years, it is possible to use a protective layer that is 10 mm thinner than that indicated in Table 6.

39/68 If necessary, the thickness of the protective layer of grout, mortar or concrete inside a permanent casing can be reduced by 10 mm, provided that the wall thickness of the casing is greater than 4 mm. In an aggressive environment, corrosion protection should be provided by a greater protective layer thickness than that indicated in Table 6 a higher corrosion allowance for the steel cross-section organic or inorganic coatings a permanent casing cathodic protection

7.5.3 Corrosion allowance of steel-surfaced drilled piles Surrounding conditions are to be taken into account in the corrosion protection of drilled piles. Corrosion is usually taken into account in the form of the so-called corrosion allowance. Corrosion allowance depends on the designed service life of the structure and estimated corrosion rate. In clean soil corrosion is generally so low that the protection of piles can be achieved by increasing wall thickness. Table 7 presents the corrosion allowances recommended in Eurocode 3, Part 5: Piling. Because of the higher safety requirements of bridges, the Finnish Road Administration uses the values given in Table 8. If piles are exposed to anti-icing salt, corrosion protection or corrosion allowance must be determined separately. Under difficult corrosion conditions, such as in contaminated soil or air, corrosion protection can be achieved, for instance, by a concrete structure. Separate protection can also be attained by painting or using epoxy or polyethylene coatings or cathodic protection. If these protection methods are used, their strength during installation must be taken into account. If piles are installed into rocky or otherwise scratching soil, coatings may be damaged. The rate of the resulting spotty corrosion is markedly higher than the rate of even corrosion. If cathodic protection is used, its service life should be taken into account. Table 7. Oversizing of steel parts for corrosion [mm] SFS-ENV 1993-5:1997According to

Eurocode 3:- 5 Piling. Soil conditions Service life (years) 5 25 50 75 100 Undisturbed natural soil (sand, silt, clay)

0.00

0.30

0.60

0.90

1.20

Contaminated natural soil and industrial areas

0.15

0.75

1.50

2.25

3.00

Aggressive natural soil (marsh, bog, peat)

0.20

1.00

1.75

2.50

3.25

Non-compacted non-aggressive fill (sand, clay, silt)

0.18

0.70

1.20

1.70

2.20

Non-compacted aggressive fill (ash, slag)

0.50

2.00

3.25

4.50

5.70

- Compacted fill has a slower corrosion rate than non-compacted fill. With compacted fill the corrosion allowance of non-compacted fill can be divided by two. - The values are recommendations. Local conditions must always be taken into account. - The values for a service life of 5 or 25 years are based on measurements. Other values were obtained by linear extrapolation and are therefore on the safe side. Furthermore, Appendix F. Bearing Piles, section 2 mentions that corrosion in air in 100 years is 1mm in a normal climate 2 mm near the sea

40/68 Table 8. Oversizing of steel parts for corrosion by the Finnish Road Administration